The present invention relates generally to methods and systems for interfacing between circuit network switches and ATM edge switches and, more particularly, to a method and system for interfacing a circuit switch trunk side to support a consolidated trunk group to an ATM edge switch while conforming to existing circuit switch design constraints.
Current telephone networks as well as their associated transmission media, routing, and cross connection devices are digital circuit switched facilities. Routing of user information, e.g., voice and voice band data services, from a source to a destination is via an end to end switched connection. The connection is dedicated for the duration of a call using the connection. That is, the call is set up over a link interconnecting origination and destination switches. As such, the connection lasts only for the duration of the call.
In telecommunications systems, a vehicle offering a range of different bandwidth services is based on Asynchronous Transfer Mode (ATM) protocols. These protocols define a particular data structure called a cell. A cell is a data packet of a fixed size (53 octets). A cell is formed by a header (5 octets) and payload (48 octets) for transporting routing and user information. In contrast to circuit switched networks, an ATM network shares a connection asynchronously.
A telephony local exchange carrier network includes central offices each of which may be, for example, the No. 5ESS switch available from Lucent. The No. 5ESS switch is described in the ATandT Technical Journal, Vol. 64, No. 6, July/August 1985, pages 1303-1564. Many telephony local exchange carriers are planning to evolve from a circuit switched network to an ATM backbone environment to carry voice traffic. In such a telecommunications system, the ATM backbone network connects the central offices. Each central office switch of the circuit network is connected to a respective ATM edge switch of the ATM backbone network. An ATM edge switch is a switch which sits at the edge of the ATM backbone network, providing access from the circuit network to the ATM network.
The circuit switched network in larger metropolitan areas is almost full mesh with point to point trunk groups in multiples of T1s. A trunk group is a group of trunks or circuits that make a connection between two switches. A full mesh network is a network in which each switch has a dedicated connection to all of the other switches. T1 (or DS1) stands for trunk level 1 and is a digital transmission link in which a 1.544 million bits per second are carried to handle 24 voice conversations, i.e., 24 DS0s. A DS0 stands for digital service level 0 and is 64,000 bits per second which is the standard speed for digitizing one voice conversation using pulse code modulation (PCM). Thus, for an area with 40 switches the full mesh network includes roughly 40*39/2=780 separate trunk groups that must be managed and provisioned. There may be more than one trunk group between switches.
Class 5 switches such as the No. 5ESS switch can handle trunk groups having up to approximately 2,000 (1,952) trunks under existing switch design constraints. However, what is needed to support a hub type ATM network is a provisioning configuration for interfacing a class 5 switch to support a consolidated trunk group having more than 2,000 trunks to an ATM edge switch.
Accordingly, it is an object of the present invention to provide a method and system for interfacing a circuit switch to support a consolidated trunk group to an ATM edge switch while conforming to existing circuit switch design constraints.
It is another object of the present invention to provide a method and system for configuring a class 5 switch to support a consolidated trunk group having more than 2,000 trunks to an ATM edge switch.
It is a further object of the present invention to provide a method and system for configuring a class 5 switch to support a large virtual trunk group of up to 11,712 trunks while avoiding glare.
In carrying out the above objects and other objects, the present invention provides a method for configuring a class 5 switch of a switch network to support a virtual trunk group to an ATM edge switch of an ATM network while avoiding glare. The class 5 switch provides one trunk group and has an overflow feature for providing overflow trunk groups. Each trunk group has trunks for handling calls. The method includes initiating the overflow feature of the class 5 switch to provide at least one overflow trunk group. The primary trunk group of the class 5 switch is then provisioned as an outgoing primary trunk group for outgoing calls. One of the overflow trunk groups of the class 5 switch is then provisioned as an incoming primary trunk group for incoming calls. The outgoing primary trunk group is then hunted through to seize trunks for outgoing calls. The incoming primary trunk group is then hunted through to seize trunks for incoming calls.
Preferably, the class 5 switch is a No. 5ESS switch, a Nortel DMS switch, and the like. The at least one overflow trunk group includes at least two overflow trunk groups. The method preferable includes provisioning all of the non-primary trunk groups of the at least two overflow trunk groups as overflow trunk groups for outgoing and incoming calls. An overflow trunk group is hunted through to seize trunks for outgoing calls after all of the trunks of the outgoing primary trunk group have been seized. The overflow trunk group is also hunted through to seize trunks for incoming calls after all of the trunks of the incoming primary trunk group have been seized.
Alternatively, the at least one overflow trunk group includes at least three overflow trunk groups. The method alternatively includes provisioning all of the non-primary trunk groups of the at least three overflow trunk groups as overflow trunk groups for outgoing and incoming calls. A first overflow trunk group is then hunted through to seize trunks for outgoing calls after all of the trunks of the outgoing primary trunk have been seized. A second overflow trunk group is then hunted through to seize trunks for outgoing calls after all of the trunks of the outgoing primary trunk group and the first overflow trunk group have been seized. The second overflow trunk group is then hunted through to seize trunks for incoming calls after all of the trunks of the incoming primary trunk group have been seized. The first overflow trunk group is then hunted through to seize trunks for incoming calls after all of the trunks of the incoming primary trunk group and the second overflow trunk group have been seized.
Further, in carrying out the above objects and other objects, the present invention provides a telecommunications system includes a circuit switch network having a class 5 switch. The class 5 switch provides one trunk group and has an overflow feature for providing at least three overflow trunk groups. An ATM network having an ATM edge switch is connected to the class 5 switch for receiving and transmitting calls to the circuit switch network.
A controller is operable for initiating the overflow feature of the class 5 switch to provide at least one overflow trunk group, for provisioning the primary trunk group of the class 5 switch as an outgoing primary trunk group for outgoing calls, and for provisioning one of the overflow trunk groups of the class 5 switch as an incoming primary trunk group for incoming calls. The controller is further operable for provisioning the non-primary overflow trunk groups as overflow trunk groups for outgoing and incoming calls. The controller is also operable for hunting through the outgoing primary trunk group to seize trunks for outgoing calls, hunting through the incoming primary trunk group to seize trunks for incoming calls, hunting through a first overflow trunk group to seize trunks for outgoing calls after all of the trunks of the outgoing primary trunk group have been seized, and hunting through a second overflow trunk group to seize trunks for incoming calls after all of the trunks of the incoming primary trunk group have been seized.
The controller is further operable for hunting through the second overflow trunk group to seize trunks for outgoing calls after all of the trunks of the outgoing primary trunk group and the first overflow trunk group have been seized and for hunting the first overflow trunk group to seize trunks for incoming calls after all of the trunks of the incoming primary trunk group and the second overflow trunk group have been seized.
The above objects and other objects, features, and advantages of the present invention will be apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.